Method and device for preparing an implant from an implant material

ABSTRACT

A method and device for preparing an implant from an implant material are provided. A defect image of the defect which has a defect contour is made available, in which a first calibration member arranged in or adjacent to the defect is displayed. A second calibration member is arranged on or adjacent to the implant material to be processed, this second calibration member corresponding to the first calibration member. A real-time image of the implant material is displayed on a display device. The defect image is displayed on the display device and superimposed on the real-time image so that the first and the second calibration members are displayed one on top of the other. A processing tool is displayed on the display device in the real-time image and moved over the implant material so that it follows the defect contour displayed in the defect image.

This application is a continuation of International application No.PCT/EP2006/068861 filed on Nov. 23, 2006.

The present disclosure relates to the subject matter disclosed inInternational application No. PCT/EP2006/068861 of Nov. 23, 2006 andGerman application No. 10 2005 058 760.7 of Dec. 5, 2005, which areincorporated herein by reference in their entirety and for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates to a method for preparing an implant froman implant material, the implant serving to fill a defect in a human oranimal body. Furthermore, the present invention relates to a device forpreparing an implant from an implant material, the implant serving tofill a defect in a human or animal body.

Implants which correspond exactly to the shape and the size of a defectare, for example, required for the treatment of cartilage defectsresulting from injuries. Implants of this type comprise, for example, acarrier which can be injected with cartilage cells from the patient'sown body. A method of the type described at the outset is described, forexample, in the German Utility Model No. 20 2005 005 085. However, anavigation system, with the aid of which a defect contour of the defectto be treated is determined with a navigated palpation instrument, isnecessary to carry out the known method. This method is complicated andcannot be carried out when a navigation system is not available.

It would therefore be advantageous to provide a method and a device forpreparing an implant from an implant material, the implant serving tofill a defect in a human or animal body, which allow the implant to beprepared in a simple manner to fit the defect exactly.

SUMMARY OF THE INVENTION

In accordance with an example embodiment of the present invention, amethod for preparing an implant from an implant material is provided inwhich a defect image of the defect which has a defect contour is madeavailable, in which a first calibration member arranged in or adjacentto the defect is displayed, that a second calibration member is arrangedon or adjacent to the implant material to be processed and correspondsto the first calibration member, that a real-time image of the implantmaterial is taken and displayed on a display device in real time, thatthe defect image made available is displayed on the display device andsuperimposed on the real-time image in such a manner that the first andthe second calibration members are displayed one on top of the other inthe same shape and size and that a processing tool is displayed in thereal-time image on the display device and moved over the implantmaterial in such a manner that it follows the defect contour displayedin the defect image on the display device.

As a result of the superimposition of the real-time image and the defectimage in such a manner that the first and the second calibration membersare displayed one on top of the other in the same shape and size, thedefect displayed on the display device corresponds to the implant to beprepared from the implant material both in its shape and in its size. Ifthe processing tool is moved over the implant material such that itfollows the defect contour displayed in the defect image on the displaydevice, the desired implant can be prepared from the implant material inexactly the size and shape which correspond to the defect. The advantageof this method is to be seen, in particular, in the fact that nonavigation system is required. Furthermore, no real-time image of thedefect need be available. This means that the method need not be carriedout either in an operating theater or by a doctor.

However, it is also eminently suitable for use in an operating theatersince only an image generating device for generating the real-time imageas well as a display device are required and they can easily be broughtinto a sterile area. On the other hand, it is not necessary to bring aprojector, with which a defect contour can be transferred onto theimplant material to be processed, into the sterile area. A calibrationmember is also to be understood as a calibration structure which isformed from several parts which are in a fixed relationship to oneanother. Furthermore, the first calibration member can also be a virtualcalibration member, i.e., a calibration structure superimposed onto thedefect image or a calibration member which corresponds to the secondcalibration member.

An areal implant is advantageously prepared from an essentially flatimplant material. In this way, cartilage implants and also skin implantsor the like can be prepared in a desired manner. The method is,therefore, suitable for preparing all types of implants which aresuitable for filling a defect in the body.

It is advantageous when a first image generating device with a firstoptical axis is used for taking the real-time image, the axis beingaligned at a first image angle relative to a plane defined by theimplant material when a defect image is made available which has beentaken with a second image generating device which has a second opticalaxis, wherein the second optical axis was aligned at a second imageangle relative to a plane defined by the defect, and when the firstimage angle is set in accordance with the second image angle. In thisway, it can be ensured that not only the defect in the defect image butalso the implant material in the real-time image are displayed on thedisplay device at the same angle. As a result, distortion errors in therepresentation of the two superimposed images on the display device areavoided and it is ensured that the implant to be prepared exactly fillsthe defect even with a distorted representation of the defect and theimplant material.

In order to avoid distortions during the representation of both thedefect and the implant material, it is favorable when the second opticalaxis was aligned at right angles or essentially at right angles to theplane defined by the defect and when the first optical axis is alignedat right angles or essentially at right angles to the plane defined bythe implant material.

In accordance with a preferred variation of the method according to theinvention, it may be provided for a defect image to be made availablewhich has been taken by scanning the defect contour with a navigatedpalpation instrument. Such a defect image has the advantage that onaccount of its generation by way of navigated scanning of the defectcontour itself a scale is known and dimensions of the defect and thedefect contour can be ascertained immediately. Furthermore, such adefect image has the advantage that a virtual calibration structure or avirtual calibration member can be superimposed onto the defect image,namely in the correct size scale. If, for example, shape and size of thefirst calibration member are known, a second calibration membercorresponding to it may be superimposed directly onto the defect imageand in the correct size scale. As a result, the arrangement of a realcalibration member in or on the defect and, therefore, the introductionof a foreign body into a human or animal body is superfluous.

It would be fundamentally conceivable for the defect image to bedisplayed on the display device as background image. It is, however,advantageous when the real-time image is displayed on the display deviceas background image and the defect image as foreground image. In bothcases, movement of the processing tool can be followed in an optimummanner.

In principle, it would be conceivable for the defect image and thereal-time image to be altered only in their size relative to one anotherso that the two calibration members are displayed in the same size. Itis, however, favorable when the defect image and the real-time image arebrought into coincidence on the display device by moving the tworepresentations relative to one another and altering an enlarging factorof the two representations relative to one another. In this simple way,the two calibration members can be displayed one on top of the other onthe display device so that it can immediately be recognized whether theyhave the same size and the same position. As a result, it is possiblefor a scale of the defect image to correspond to a scale of thereal-time image so that, without needing to use additional measurementdevices, a contour of the defect can be transferred 1:1 onto the implantmaterial.

In principle, it would be conceivable to alter the defect image in sizeand position such that the two calibration members can be brought intocoincidence on top of one another. It is, however, advantageous when thedefect image is displayed on the display device unaltered and when thereal-time image is moved relative to the defect image and is enlarged orreduced in size in such a manner that the first calibration member andthe second calibration member are displayed congruently on the displaydevice. This procedure is particularly simple since the defect imagemade available need no longer be altered whereas the real-time image,since it is taken directly as the method is being carried out, caneasily be altered, for example, also by adjusting an enlarging factor atthe first image generating device or altering a position thereofrelative to the implant material.

In order to avoid the implant to be prepared not being produced so as tofit the defect exactly, it is favorable when a flat member is used asfirst and second calibration members, respectively. As a result, anydistortions during the superimposition of the representations of the twocalibration members on the display device can be avoided.

A disc-shaped member is favorably used. A disc-shaped member has noparticularly preferential direction and so the two calibration memberscan be displayed congruently on the display device duringsuperimposition of the defect image and the real-rime image merely bymoving them in two directions at right angles to one another and byadjusting an enlarging factor.

It is advantageous when a calibration structure is used as first andsecond calibration members, respectively, this structure comprising atleast two calibration elements which are in a fixed, geometric relationto one another. This has the advantage, in particular, that thecalibration structure can be selected such that no calibration elementcan or need come directly into contact with the implant material whichcould hinder the preparation of the implant from the implant material,on the one hand, or also damage the implant material itself.

In order to increase the accuracy of the method, it is favorable when acalibration structure is used which comprises a carrier, on which two,three, four or more calibration members are arranged. In particular, thecalibration elements can be arranged at a considerable distance from oneanother, whereby accuracy during the superimposition of the defect imageand the real-time image can be increased.

The real-time image may be generated particularly easily when a digitalvideo camera is used as first image generating device.

In order to be able to process the defect image in a simple manner witha data processing device, it is favorable when a defect image generatedwith a digital camera is used. This makes it possible to display thedefect image directly on the display device and to superimpose it withan additional digital image, for example, the real-time image.

In accordance with a preferred variation of the method according to theinvention, it may be provided for the defect image to be taken with thesecond image generating device prior to the preparation of the implantand for the second calibration member to be arranged in or adjacent tothe defect prior to the defect image being taken. In this way, it ispossible to generate a desired defect image which is required in orderto prepare the desired implant.

In order to avoid a calibration member needing to be moved close to thedefect at all, it is favorable when the defect image is taken with thesecond image generating device prior to the preparation of the implantand when the second calibration member is superimposed onto the defectimage in or adjacent to the defect after the defect image has beentaken. It is not, therefore, a real but rather a virtual secondcalibration member which is used, for example, also in the form of acalibration structure. The second calibration member corresponds, on theother hand, to the first calibration member, wherein the secondcalibration member is selected in shape and size and displayed such thatit corresponds to a representation of the first calibration member inthe defect image, taking the enlarging scale of the defect image intoconsideration. The second image generating device can comprise, inparticular, a navigation system in conjunction with a navigatedpalpation instrument, with which a contour, i.e., a defect contour ofthe defect can be scanned and stored. The data ascertained in this waymay be displayed in the form of a defect image, for example, on ascreen.

Distortions occurring when taking the defect image and distortions ofthe defect are avoided when the second image generating device isaligned for taking a defect image in such a manner that its optical axisis aligned at right angles or essentially at right angles to a planedefined by the defect.

A digital camera is advantageously used as second image generatingdevice. This can be connected, for example, to an endoscope so thatdefect images can also be taken, in particular, from the interior of ahuman or animal body even during a minimally invasive procedure, forexample, within the scope of an arthroscopy of a knee joint.

A processing path corresponding to the defect contour is advantageouslydrawn onto the implant material with the processing tool. The defectcontour is then recognizable on the implant material and the implant tobe prepared can be separated from the implant material, for example, bycutting.

The defect contour may be transferred to the implant materialparticularly easily when a marking pen for marking the processing pathon the implant material is used as processing tool. A marking pen ispreferably used, with which a contour can be drawn onto the implantwithout damaging it.

Alternatively, it can also be advantageous when the implant to beprepared is cut out of the implant material with the processing tool.The implant can, therefore, also be prepared without the processing pathbeing marked on the implant material, whereby an additional method stepcan be saved.

A cutting tool is favorably used as processing tool. As a result, theimplant may be separated from the implant material without any problem.

It is favorable when a laser or a scalpel is used as cutting tool.Cutting tools of this type are especially suitable for separating animplant from an implant material.

In order to be able to treat a cartilage defect, for example, in a kneejoint in a desired manner, it is favorable when a cartilage replacementimplant is prepared from a cartilage replacement implant material withthe method. For example, the cartilage replacement implant material canbe a carrier material which is injected with autologous chondrocyteswhich have been grown in the laboratory after previously being removedfrom the body of the patient.

In addition, in accordance with a further example embodiment of thepresent invention, a device for preparing an implant from an implantmaterial is provided which comprises an input device for transferring adefect image of the defect which has a defect contour to the device,wherein a first calibration member arranged in or adjacent to the defectis displayed on the defect image, wherein a first image generatingdevice is provided for taking a real-time image of a second calibrationmember arranged on or adjacent to the implant material to be processed,wherein the first calibration member corresponds to the secondcalibration member, wherein a display device is provided for displayingand superimposing the real-time image and the defect image, wherein thedevice is designed in such a manner that the first and the secondcalibration members can be displayed with the display device one on topof the other in the same shape and size and wherein a processing toolwhich can be moved along the defect contour displayed in the defectimage can, at the same time, be displayed with the display device inreal time.

It is possible with the device according to the invention to process animplant material without the aid of a navigation system such that animplant can be prepared which fits the defect to be filled exactly inshape and size.

In accordance with a preferred embodiment of the invention, it may beprovided for the device to comprise a data processing device and for thedata processing device to be designed to interact with the input deviceand with the first image generating device. For example, the dataprocessing device can be designed in the form of a computer which candisplay data on a display device, for example, a monitor. The inputdevice can be designed, in particular, in the form of a reading devicefor data recording media, for example, in the form of a CD drive or amemory card reading device for memory cards, such as those used, forexample, in digital cameras. Alternatively, it would also be conceivableto provide the input device in the form of a digital port on the dataprocessing device in order to read in signals directly from a digitalcamera.

The data processing device is advantageously designed in such a mannerthat the defect image and/or the real-time image can be displayed on thedisplay device so as to be alterable in their size and position. Forexample, the data processing device can be equipped with correspondingsoftware, with which the image processing required for altering size andposition of an image can be carried out.

It is favorable when one of the methods according to the inventiondescribed above can be carried out with the device.

The following description of a preferred embodiment of an inventionserves to explain the invention in greater detail in conjunction withthe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: shows a schematic illustration while a defect image is beingtaken;

FIG. 2: shows an illustration of an example of a defect image and areal-time image, each with a calibration member;

FIG. 3: shows a schematic illustration of the superimposition andcalibration of the defect image and the real-time image; and

FIG. 4: shows a schematic illustration during the processing of theimplant material for preparing the desired implant.

FIG. 5: shows an additional, schematic illustration of a variation ofthe method for the processing of the implant material for preparing thedesired implant.

DETAILED DESCRIPTION OF THE INVENTION

The method according to the invention described above and the deviceaccording to the invention will be explained in greater detail in thefollow in conjunction with FIGS. 1 to 4, on the basis of a preferredembodiment.

In FIG. 1, an arrangement is illustrated schematically, showing how,within the scope of a minimally invasive procedure, namely in the formof an arthroscopic procedure, a defect image is, for example, taken in aknee joint 10 of a human body. For this purpose, an endoscope 12 ispreferably introduced into an open knee joint 10 once the knee joint 10has been opened up and a shaft 18 of the endoscope 12, which iselongated and defines an optical axis 16, is brought up close to adefect 20 of an articular cartilage 22 with the end 14. Prior to animage of the defect being taken, a calibration member in the form of aflat disc 24 is placed in the defect 20. An image generating device inthe form of a digital camera 26 is arranged at the proximal end of theshaft 18 of the endoscope 12, aligned with the optical axis 16 of theshaft 18. Either a light guide which is not illustrated or an opticaldevice which is not illustrated is arranged in the interior of the shaft18, by means of which it is possible to take a defect image 30 of thedefect 20 with the digital camera 26.

The defect image 30 is illustrated to the left in FIG. 2 and shows boththe defect 20 and also the disc 24 arranged within the defect 20. Adefect contour 32, i.e., a boundary line between degeneratecartilaginous tissue and healthy articular cartilage 22 is easy torecognize.

The defect image 30 is stored in a storage device 28 of the digitalcamera 26, for example, a memory card which can be inserted into a cardreading slot 34 of a computer 36 forming a data processing device andfrom which the stored defect image 30 can then be transferred to thecomputer 36. The computer 36 is part of a processing device providedaltogether with the reference numeral 38 for the preparation of animplant from an implant material. Normally, the computer 36 is connectedto a keyboard 40 and a mouse 42, via which an operator can start andoperate programs. A screen 44 serving as display device is likewiseconnected to the computer 36 and serves to display the defect image 30.

In addition, a digital video camera 46 is connected to the computer 36as additional image generating device, with which a real-time image canbe taken and displayed on the screen 44 by means of the computer 36.

For the preparation of an implant which can be inserted into the defect20 in order to fill this with an exact fit and thus make a regenerationof the damaged cartilaginous tissue possible, the video camera 46 isaligned with its optical axis 50 essentially at right angles to a planedefined by an implant material 54 stored in a flat pan 52. An additionalcalibration member in the form of a calibration disc 56 is placed on theimplant material 54. The calibration disc 56 and the disc 24 are of anidentical design, not only in their diameter but also in their height.The real-time image 48 thus generated is displayed on the screen 44, ascan be seen in FIG. 2 to the right.

While the real-time image 48 is being taken, attention is paid to thefact that the optical axis 50 is aligned relative to a plane defined bythe implant material 54 at the same angle as the optical axis 16 whilethe defect image 30 is being taken, i.e., in the same way as the opticalaxis relative to a plane defined by the defect 20. Preferably, the twooptical axes 16 and 50 are each aligned at right angles not only to theimplant material 54 but also to the defect 20.

Since, during the arrangement of the video camera 46, consideration isnot given to the distance, at which it is positioned from the implantmaterial 54, the representations of the defect image 30 and thereal-time image 48 do not normally correspond with respect to their sizescale. This is shown by the fact that the disc 24 which is identical inshape and size to the calibration disc 56 is displayed differently onthe screen 44, namely, as illustrated in FIG. 2 by way of example,smaller.

If the defect image 30 and the real-time image 48 are superimposed onthe screen 44, as illustrated in FIG. 3 to the left, neither positionnor size of the disc 24 and the calibration disc 56 correspond. Whetherthe real-time image 48 or the defect image 30 are displayed in theforeground or in the background on the screen 44 is, in principle, of noconsequence.

In order to prepare an implant 58 which corresponds to the defect 20 inshape and size, the defect image 30 and the real-time image 48 must beadjusted to one another, namely in such a manner that at least the sizeof the disc 24 corresponds to the size of the calibration disc 56. Theyneed not necessarily overlap. This may, however, be achieved in aparticularly simple manner in that the disc 24 and the calibration disc56 are brought into coincidence. This is carried out by means of anadjusting procedure which is designated symbolically in FIG. 3 by thearrow 60. For example, the real-time image 48 can be moved in twodirections at right angles to one another so that, as a result of thisdisplacement 62, the disc 24 is superimposed on the calibration disc 56on the screen 44 such that their center points are located on top of oneanother. In addition, as a result of alteration of an enlarging factor64 of a representation of the real-time image 48 on the screen 44, thesize of the calibration disc 56 can be altered such that it correspondsto the size of the disc 24. The adjusting procedure 60 is completed whenonly one circle formed by the disc 24 and the calibration disc 56 is tobe seen on the screen 44. As a result of the adjusting procedure 60, theimplant material 54 is displayed on the screen 44 in the same scale asthe defect 20.

As a result of the optimized representation of the real-time image 48and the defect image 30 on the screen 44, as illustrated in FIG. 3,everything is now ready for the preparation of the implant 58 from theimplant material 54. For this purpose, a processing tool 66, forexample, a marking pen or a scalpel is used. If a marking pen is used,this is moved over the implant material 54 with its tip 86 such that therepresentation of the processing tool 66 in the real-time image 48 onthe screen 44 follows the defect contour 32. A path of movement 70 isthus drawn on the implant material 54 and this corresponds in shape andsize to the defect contour 32. For this purpose, either an operator canmove the processing tool 66 over the implant material 54 such that theoperator moves the tip 68 of the processing tool 66 over the implantmaterial 54 following the defect contour 32 only by looking at thescreen 44. Alternatively, a device could also be provided which movesthe processing tool 66 over the implant material 54, wherein movement ofthis device is controlled and regulated as a function of the position ofthe processing tool 66 in the real-time image 48, namely such that theprocessing tool 66 always follows the defect contour 32. It would thenbe possible to prepare the implant 58 completely automatically from theimplant material 54.

As already mentioned, the processing tool 66 can also be designed in theform of a cutting tool, for example, a scalpel so that an operator or acorrespondingly suitable device can separate the implant 58 from theimplant material 54 directly in the manner described.

The method described can be carried out by anybody since it need notnecessarily be carried out in an operating theater. If a defect image 30is made available, the implant 58 can be prepared from the implantmaterial 54 at any optional location.

Alternatively, the adjusting procedure 60 can be carried out such thatthe real-time image 48 is displayed on the screen 44 unaltered and thedefect image 30 is superimposed on the real-time image by way ofdisplacement and adjustment of an enlarging factor for such a time untilthe disc 24 and the calibration disc 56 are displayed congruently one ontop of the other.

In the following, a second variation of the method according to theinvention which is modified somewhat in comparison with the methoddescribed above will be explained in greater detail in conjunction withFIG. 5, with a second embodiment of a device according to the invention.

The second variation of the method according to the invention differsfrom the variation described above in that in order to take the defectimage no calibration member and also no calibration structure is placedin the defect 20. Instead, a calibration member in the form of a virtualcalibration structure 24′ is superimposed directly onto the defect image30 after the defect image 30 has been taken or during the processing ofthe implant material 54. The calibration structure 24′ comprises, in thepresent case, four solid points arranged in a square. Instead of thecalibration disc 56 forming a second calibration member, a realcalibration structure 56′ is used which is formed by a square frame 78′,from which four identical calibration discs 74′ protrude out of theplane defined by the frame 78′, wherein a side length 72′ of the frame78′ has a predetermined value, for example, a length of 10 cm.

The virtual calibration structure 24′ is, with a known resolution and aknown scaling of the defect image 30, superimposed onto this image insuch a manner that four virtual calibration discs 76′ arranged in theshape of a square structure are to be seen, their displayed distances inrelation to the defect 20 corresponding to the side length 72′. Since anenlarging factor of the defect image 30 need not necessarily correspondto an enlarging factor of the real-time image 48, the actual size of thecalibration structure 24′ superimposed on the defect image 30 can differfrom the size of the calibration structure 56′ displayed in thereal-time image 48. As a result of corresponding alteration of anenlarging factor 64 of a representation of the real-time image 48 on thescreen 44 as well as corresponding alteration of the positions of thereal-time image 48 and the defect image 30 relative to one another, thecalibration structure 24′ can be superimposed on the calibrationstructure 56′ such that only one single calibration structure 24′ and56′, respectively, is still visible for an observer. The defect contour32 is, as already described in conjunction with FIG. 4, transferredvirtually on the screen 44 onto the implant material 54 which isprepared with a processing tool 66, the movement of which can befollowed in the real-time image 48 displayed on the screen 44 and,therefore, the implant 58 prepared, either by hand or fullyautomatically.

Alternatively, it is also possible to generate the defect image byscanning the defect contour 32 with a navigated palpation instrument,the movement of which can be traced with a navigation system. This hasthe advantage, in particular, that no optical image generating device isrequired for taking the defect image and, in addition, the calibrationstructure 24′ can be superimposed virtually onto the defect image 30 inthe correct scale since the enlarging scale can also be ascertained andmade available immediately by a navigation system during the navigatedscanning of the defect contour 32.

1. Method for preparing an implant from an implant material, saidimplant serving to fill a defect in a human or animal body, wherein adefect image of the defect having a defect contour is made available, afirst calibration member arranged in or adjacent to the defect beingdisplayed in said image, wherein a second calibration member is arrangedon or adjacent to the implant material to be processed, said secondcalibration member corresponding to the first calibration member,wherein a real-time image of the implant material is taken and displayedin real time on a display device, wherein the defect image madeavailable is displayed on the display device and superimposed on thereal-time image in such a manner that the first and the secondcalibration members are displayed one on top of the other in the sameshape and size and wherein a processing tool is displayed in thereal-time image on the display device and moved over the implantmaterial in such a manner that it follows the defect contour displayedin the defect image on the display device.
 2. Method as defined in claim1, wherein an areal implant is prepared from an essentially flat implantmaterial.
 3. Method as defined in claim 1, wherein a first imagegenerating device with a first optical axis is used for taking thereal-time image, said axis being aligned at a first image angle relativeto a plane defined by the implant material, wherein a defect image ismade available, said image having been taken with a second imagegenerating device having a second optical axis, wherein the secondoptical axis was aligned at a second image angle relative to a planedefined by the defect, and wherein the first image angle is set inaccordance with the second image angle.
 4. Method as defined in claim 3,wherein the second optical axis was aligned at right angles oressentially at right angles to the plane defined by the defect andwherein the first optical axis is aligned at right angles or essentiallyat right angles to the plane defined by the implant material.
 5. Methodas defined in claim 1, wherein a defect image is made available, saidimage having been taken by scanning the defect contour with a navigatedpalpation instrument.
 6. Method as defined in claim 1, wherein thereal-time image is displayed on the display device as background imageand the defect image as foreground image.
 7. Method as defined in claim1, wherein the defect image and the real-time image are brought intocoincidence on the display device by moving the two representationsrelative to one another and altering an enlarging factor of the tworepresentations relative to one another.
 8. Method as defined in claim7, wherein the defect image is displayed on the display device unalteredand wherein the real-time image is moved and enlarged or reduced in sizerelative to the defect image in such a manner that the first calibrationmember and the second calibration member are displayed congruently onthe display device.
 9. Method as defined in claim 1, wherein a flatmember is used as first and second calibration members, respectively.10. Method as defined in claim 9, wherein a disc-shaped member is used.11. Method as defined in claim 1, wherein a calibration structure isused as first and second calibration members, respectively, saidstructure comprising two calibration elements in a fixed, geometricrelation to one another.
 12. Method as defined in claim 11, wherein acalibration structure comprising a carrier is used, two, three, four ormore calibration elements being arranged on said carrier.
 13. Method asdefined in claim 3, wherein a digital video camera is used as firstimage generating device.
 14. Method as defined in claim 3, wherein adefect image generated with a digital camera is used.
 15. Method asdefined in claim 3, wherein prior to the preparation of the implant thedefect image is taken with the second image generating device andwherein prior to the defect image being taken the second calibrationmember is arranged in or adjacent to the defect.
 16. Method as definedin claim 3, wherein prior to the preparation of the implant the defectimage is taken with the second image generating device and wherein afterthe defect image has been taken the second calibration member issuperimposed onto the defect image in or adjacent to the defect. 17.Method as defined in claim 15, wherein in order to take the defect imagethe second image generating device is aligned in such a manner that itsoptical axis is aligned at right angles or essentially at right anglesto a plane defined by the defect.
 18. Method as defined in claim 3,wherein a digital camera is used as second image generating device. 19.Method as defined in claim 1, wherein a processing path corresponding tothe defect contour is drawn onto the implant material with theprocessing tool.
 20. Method as defined in claim 19, wherein a markingpen for marking the processing path on the implant material is used asprocessing tool.
 21. Method as defined in claim 1, wherein the implantto be prepared is cut out of the implant material with the processingtool.
 22. Method as defined in claim 21, wherein a cutting tool is usedas processing tool.
 23. Method as defined in claim 22, wherein a laseror a scalpel is used as cutting tool.
 24. Method as defined in claim 1,wherein a cartilage replacement implant is prepared from a cartilagereplacement implant material with the method.
 25. Device for preparingan implant from an implant material, said implant serving to fill adefect in a human or animal body, comprising an input device fortransferring a defect image of the defect having a defect contour to thedevice, wherein a first calibration member arranged in or adjacent tothe defect is displayed on the defect image, wherein a first imagegenerating device is provided for taking a real-time image of a secondcalibration member arranged on or adjacent to the implant material to beprocessed, wherein the first calibration member corresponds to thesecond calibration member, wherein a display device is provided fordisplaying and superimposing the real-time image and the defect image,wherein the device is designed in such a manner that the first and thesecond calibration members are adapted to be displayed with the displaydevice one on top of the other in the same shape and size and wherein aprocessing tool movable along the defect contour displayed in the defectimage is adapted to be displayed at the same time with the displaydevice in real time.
 26. Device as defined in claim 25, wherein thedevice comprises a data processing device and wherein the dataprocessing device is designed to interact with the input device and withthe first image generating device.
 27. Device as defined in claim 26,wherein the data processing device is designed in such a manner that thedefect image and/or the real-time image are adapted to be displayed onthe display device so as to be alterable in their size and position. 28.Device as defined in claim 25, wherein a method for preparing an implantfrom an implant material, said implant serving to fill a defect in ahuman or animal body, wherein a defect image of the defect having adefect contour is made available, a first calibration member arranged inor adjacent to the defect being displayed in said image, wherein asecond calibration member is arranged on or adjacent to the implantmaterial to be processed, said second calibration member correspondingto the first calibration member, wherein a real-time image of theimplant material is taken and displayed in real time on a displaydevice, wherein the defect image made available is displayed on thedisplay device and superimposed on the real-time image in such a mannerthat the first and the second calibration members are displayed one ontop of the other in the same shape and size and wherein a processingtool is displayed in the real-time image on the display device and movedover the implant material in such a manner that it follows the defectcontour displayed in the defect image on the display device, is adaptedto be carried out with the device.